1. Field of the Invention
Aircraft Propulsion Assembly.
2. Description of the Prior Art
A Rumanian born engineer Coanda discovered some years ago that a fluid flow phenomena occured when fluid is ejected rapidly over the lip of an orifice into a moving stream of fluid, which results in a lowering of the co-efficient of drag of the fluid stream.
A major object of the present invention is to provide an aircraft propulsion assembly that takes advantage of the Coanda effect to increase the thrust generated by a rearwardly moving stream of air, by increasing the velocity of the rearwardly moving stream without increasing the power of the prime mover that generates the air stream.
Another object of the invention is to supply a power driven rotating air stream generating element that rotates within a circular housing, with a first portion of the air stream being directed rearwardly through the nozzle, and a second portion of the air stream through a series of circumferentially spaced slots into a plenum chamber. The second portion of air discharged into the plenum chamber is compressed and discharges through an orifice in the plenum chamber into the forward portion of the nozzle at a higher velocity than the first portion of the rearwardly moving air stream. The second portion of the air forms a sheath of air within the nozzle that is moving rearwardly therein at a higher velocity than the first portion of air, and as a result the drag imposed on the rearwardly moving first portion of air is reduced to a minimum, and the first portion of air discharges from the nozzle at maximum velocity to provide maximum thrust to the assembly. The air stream generating element not only provides the first portion of air that is directed rearwardly through the nozzle for thrust generating purposes, but also the compressed air in the plenum chamber that escapes therefrom at a higher velocity and due to the Coanda effect insulates the first portion of air from drag resistance in moving rearwardly through the nozzle to increase the efficiency of the thrust generated by the assembly.